Abstract: The present application discloses a composite substrate with a protective layer for preventing metal from diffusing, comprising: a thermally and electrically conductive layer (2) having a melting point of greater than 1000° C., and a GaN mono-crystalline layer (1) located on the thermally and electrically conductive layer (2). At least the side wall of the composite substrate is cladded with a protective layer (3) for preventing metal from diffusing. The composite substrate not only takes account of the homoepitaxy required for GaN epitaxy and improves the quality of the crystals, but also can be used directly to prepare LEDs with vertical structures and significantly reduce costs. The disclosed composite substrate effectively avoids the pollution of experimental instruments by the diffusion and volatilization of a metal material during the growth of MOCVD at high temperature.

Abstract: The present application discloses a composite substrate with a protective layer for preventing metal from diffusing, comprising: a thermally and electrically conductive layer (2) having a melting point of greater than 1000° C., and a GaN mono-crystalline layer (1) located on the thermally and electrically conductive layer (2). At least the side wall of the composite substrate is cladded with a protective layer (3) for preventing metal from diffusing. The composite substrate not only takes account of the homoepitaxy required for GaN epitaxy and improves the quality of the crystals, but also can be used directly to prepare LEDs with vertical structures and significantly reduce costs. The disclosed composite substrate effectively avoids the pollution of experimental instruments by the diffusion and volatilization of a metal material during the growth of MOCVD at high temperature.

Abstract: The present application discloses a composite substrate used for GaN growth, comprising a thermally and electrically conductive layer (1) with a melting point greater than 1000° C. and a mono-crystalline GaN layer 2 (2) located on the thermally and electrically conductive layer (1). The thermally and electrically conductive layer (1) and the mono-crystalline GaN layer 2 (2) are bonded through a van der Waals force or a flexible medium layer (3). The composite substrate can further include a reflective layer (4) located at an inner side, a bottom part, or a bottom surface of the mono-crystalline GaN layer 2. In the disclosed composite substrate, iso-epitaxy required by GaN epitaxy is provided; crystalline quality is improved; and a vertical structure LED can be directly prepared. Further, a thin mono-crystalline GaN layer 2 greatly reduces cost, which is advantageous in applications.

Abstract: A method for preparing a composite substrate for GaN growth includes: growing a GaN monocrystal epitaxial layer on a sapphire substrate, bonding the GaN epitaxial layer onto a temporary substrate, lifting off the sapphire substrate, bonding the GaN epitaxial layer on the temporary substrate with a thermally and electrically conducting substrate, shedding the temporary substrate, and obtaining the composite substrate in which the GaN layer having a surface of gallium polarity is bonded to the conducting substrate. If the GaN layer on the sapphire substrate is directly bonded to the conducting substrate, after the sapphire substrate is lifted off, a composite substrate in which a GaN epitaxial layer having a surface of nitrogen polarity is bonded to the conducting substrate. The disclosed composite substrates have homoepitaxy and improved crystal quality; they can be used for forming LED and other devices at greatly reduces costs.